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Both artificial shading and evaporative cooling have proven to be effective strategies for improve outdoor thermal comfort. However, their combined effect on microclimates or thermal sensations has rarely been investigated, hindering our understanding of the interactions among cooling strategies. In this study, we tested the performance of sun sails with different coverage ratios, mist-spray systems with different nozzle arrangements, and a combination of these two strategies for cooling a kindergarten courtyard using validated ENVI-met models. Among the strategies, we found that the shade + mist strategy is the most effective and can reduce the physiological equivalent temperature (PET) by up to 14.43 °C and heat stress levels by 2–3 categories in originally exposed areas. This was followed by the sun sail shading strategy. The mist-spray system had a relatively weak cooling effect. The cooling effects of sun sails increased with coverage ratios and mounting heights, whereas the spatial cooling distribution of mist spraying was mainly determined by wind rather than by nozzle arrangements. In addition, we found that shading can enhance the cooling effect of mist spraying in terms of air temperature, but reducing its cooling effect in terms of the mean radiant temperature. Our results highlight a great potential of comprehensively using multiple strategies to improve outdoor thermal comfort, and provide a design basis for enhancing thermal comfort in similar school courtyards in Hunan Province in China. [Display omitted] • Sun sail is more effective than mist for improving thermal comfort in the courtyard. • The combination of shading and mist spraying further improves thermal comfort. • Shading redistributed mist-spray cooling effects between the air and the ground. • Wind, rather than nozzle arrangement, determines the cooling distribution of mist. • The cooling effects of sun sails increased with coverage ratio and mounting height. [ABSTRACT FROM AUTHOR]

This study predicts the thermal performance of office buildings using Direct Evaporative Cooling (DEC) systems for thermal comfort during the summer season of Indian composite climate. For this purpose, thermal monitoring of office buildings using DEC systems was carried out for peak summer months (April to July 2016) in Jaipur city. Experimental results were utilized to calibrate the thermal simulation models, developed using EnergyPlus. Taguchi design was further applied to develop L 16 Orthogonal array of control factors and their respective levels for performing simulation runs. Simulation run outputs were then used for predicting supply air temperature and indoor air temperature as a function of independent variables (control factors) using Multiple Linear Regression technique. Statistical significance of temperature correlations was established using Analysis of Variance. Field validation from two other buildings (of similar characteristics) found a reasonably good agreement (R2 > 0.90) between the onsite measurements and the computed values of indoor temperature. The same methodology was also repeated to suggest mathematical correlations for specific humidity prediction of supply air and then indoor air. Finally, the potential of DEC to offset thermal discomfort was assessed using the proposed mathematical correlations. This was accomplished by plotting the predicted indoor conditions on Composite Climate-specific Adaptive Thermal Comfort Zone (CCATCZ) developed by the authors particularly for office buildings of Indian composite climate. Comfort prediction with ASHRAE Standard 55–2013 thermal comfort zone and CCATCZ revealed that approximately 42% and 52% of the thermal discomfort hours could be evaded with the use of DEC during the summer season. • Thermal monitoring of buildings using DEC systems is performed. • Taguchi L 16 OA is adopted for performing simulation runs. • Mathematical correlations for prediction of supply air conditions and indoor environment are presented. • Around 52% of discomfort can be eliminated with DEC in Indian composite climate. [ABSTRACT FROM AUTHOR]

A spray Passive Downdraft Evaporative Cooling (PDEC) system achieves great savings for space cooling and improves indoor environmental quality by supplying a large amount of fresh outdoor air. As previous studies heavily focused on the energy saving capability of a spray PDEC system due to lack of methods for a detailed analysis, the influence of cool humid supply air from a spray PDEC system in a space in buildings has not been comprehensively studied. This study is intended to evaluate the competence of a spray PDEC system as a primary cooling system in typical spaces in a primary school building by developing a method using building energy simulation tool. It runs one-day simulations in a hot dry climate and a warm moderate climate in order to distinctly examine the benefits and the areas that should be advanced. It analyses how a spray PDEC system responds to the space cooling loads and spaces conditioned by the system thermally behave. The results of the simulations affirm that a spray PDEC system is capable of conditioning building spaces in the two climates, indicating some areas to be improved. • The study develops the most accurate method to examine the impact of the system. • A water flow rate of 150l/h or greater is reasonable. • A constant supply air temperature is essential to mitigate adverse effects. • The system may be more effective to serve small building spaces. • The results suggest a finer control to maximize energy efficiency of the system. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to improve the comfort and liveability of urban open spaces during the hottest months of the summer by implementing an overhead water mist cooling system. The campaign was conducted in two different Italian urbanscapes (Ancona and Rome, representative of Cfa and Csa climates) one after the other. Monitoring data and comfort questionnaires were combined to extract useful information by means of statistical tests, regressions and data mining algorithms and, ultimately, to delineate design and operating guidelines to maximize people's satisfaction with the misted environment. The cloud of droplets reduced the temperature and the UTCI by 8.2 °C and 7.9 °C respectively, against a 7% mean humidity premium. The vertical cooling and humidification profiles obeyed a Lorentzian distribution, peaking within approximately 0.5 m of the injection. The severe overheating experienced outside of the cooled areas evanished under the spray, with 67% (Ancona) to 90.6% (Rome) of respondents reporting only slight bending from thermal neutrality. Perception and preferences towards solar radiation, humidity level and wind all improved within the droplets mist. In terms of comfort-oriented, optimized design criteria, the system proved to work best with a dominant and steady light breeze (1–2 m/s), in highly irradiated sites and suspended at 1.2–1.5 m above the average height of users. Image 1 • Urban comfort was experimentally investigated in two Mediterranean cities. • Water nebulization was implemented to cool down the air and comparatively assessed. • Measurements and comfort questionnaires were collected over the warmest months. • Data were interpreted via statistical tests, regressions and data mining algorithms. • Optimal design criteria for the use of nebulization in urban open spaces were derived. [ABSTRACT FROM AUTHOR]

Abstract In this work, an opportunity to improve the seasonal utilizability of an indirect evaporative cooler integrated air-conditioning system is presented. The improved design recovers the waste heat from wet air passages by supplying them to the comfort zone of produce commodities whilst supplying the dry air to human-occupants-comfort-zone i.e. operating for dual purposes. The analysis is carried out for three different configurations of indirect evaporative cooler namely counter-arrangement, cross-arrangement, and multi-zonal (advanced) heat and mass exchanging devices. The performance of each integrated air-conditioning system is presented in terms of a 'special' mixing ratio, system capacity, and energy-efficiency-ratio. Results have shown that the waste heat from the wet passages can be exploited and the seasonal utilizability factors of the proposed air-conditioning system can reach up to 1.41, 1.13 and 1.34 for counter, cross, and multi-zonal indirect-evaporative coolers respectively. Afterwards, the system analysis for different climatic conditions has shown that it offers high performance in desert and semi-arid regions. Graphical abstract Image 1 Highlights • Dual-purpose indirect-evaporative cooler integrated air-conditioner is presented. • It can meet the comfort zone of human and produce occupants. • Three configurations of indirect-evaporative coolers are analyzed. • It increases the seasonal utilizability factor to a maximum of 1.41. • It shows the best performance for dry climatic regions. [ABSTRACT FROM AUTHOR]

Abstract This study analyses the geo-climatic applicability of passive direct evaporative cooling (DEC) for improving indoor thermal comfort in the Mediterranean Region. An initial climate-dependent evaluation of the potential for implementing DEC in selected reference locations was performed using three different methodologies, including a comparison of two new key performance indicators with an existing method. The potential of DEC is then evaluated in detail by conducting thermal simulations for a prototype office building in 60 cities representing different Mediterranean climate zones, and by comparing different building configurations to analyse the influence of various design parameters on the potential for effective space cooling. Results show that the potential for increasing comfort through DEC is highly dependent on key parameters that impact the need for cooling, such as controlled natural ventilation, internal heat gains and thermal insulation. Finally, results from the initial evaluations are compared with those from the detailed building simulation to quantify the correlation between the two approaches, and to gauge the usefulness of climate-based analyses for the early evaluation of DEC applicability in a given location. The new methods for assessing the geo-climatic applicability of DEC (on an hourly basis) are shown to be feasible when compared to dynamic simulations, indicated by a significant correlation between the two. These new approaches therefore offer evaluation methods for designers considering DEC technologies during the early phases of building design. Furthermore, considering application in the study, DEC is shown to be an effective technique for low-energy cooling, especially in the Eastern Mediterranean and southern Spain. Highlights • We assess the potential of direct evaporative cooling for office design. • New methods are introduced for practical assessment of DEC potential. • Dynamic energy simulations allow comparison between indicators. • Sensitivity analysis is made on the impact of envelope characteristics. • Comfort analysis is based on temperature and relative humidity. [ABSTRACT FROM AUTHOR]

Abstract Pervious pavements are efficient in the mitigation of urban heat island effects. Many studies have revealed the water availability of pervious paving materials dominates the evaporative cooling effect. However, the water retention capacity of these materials is affected by the water absorption capability, which has scarcely been investigated in relation to evaporation. Therefore, this study investigates the water absorption capability of pervious paving materials and its influence on evaporative cooling performance. We examine the water absorption capability of three similar-coloured materials, including sintered ceramic pervious brick (CB), pervious concrete brick (PB), and open-graded pervious concrete (PC), as well as their evaporative cooling performance under a steady-state hot-humid environment in a climatic wind tunnel. The results indicate that: (1) CB had the highest water absorption coefficient of 2.04 kg/m2·s0.5, which is approximately about 30 and 200 times higher than that of PB and PC, respectively; however, these materials had similar water retention capabilities, with a capillary moisture content of 110 ± 10 kg/m3, revealing that CB could hold more water in a very short time; and (2) CB and PB could effectively reduce the surface temperature by up to 20 °C and 12 °C with a cooling period of 16 h and 12 h, respectively. In comparison, PC demonstrated a weak cooling effect of 2 °C, which only lasted for 4 h. Overall, materials with a high water absorption capability can maintain hydraulic continuity balance for a long time, which is beneficial to enhancing evaporation and further lowering the surface temperature. Highlights • High water absorption of pervious materials helps to retain enough water in a shorter time. • Water absorption capacity of pervious pavement affects the first stage of evaporation. • Materials with higher water absorption rates were more effective at cooling. [ABSTRACT FROM AUTHOR]

Abstract In a previous paper, we presented a novel approach to validate the capability of the biometeorological index, Universal Thermal Climate Index (UTCI), to predict the likelihood of urban dwellers to be outside in a public space for the heating dominated climate of Cambridge, MA. Occupancy patterns were recorded based on Wi-Fi data. The present study extends this approach to the hot and arid climate of United Arab Emirates (UAE) to evaluate the effect of outdoor evaporative coolers on resident presence in a public courtyard. Over a period of ten months, outdoor Wi-Fi access point data was collected in the public courtyard located on a university campus in Abu Dhabi. An analysis of the resulting MacID probes yields a population of 1200 regulars and 3800 visitors present in the courtyard at some point during the study period. Coincident UTCI simulations using ENVI-met strongly correlated with the number of regulars present during lunchtime both during times when the evaporative coolers were on (R2 = 75%) and off (R2 = 61%). Lunchtime attendance peaked for UTCI values in the thermal comfort range of around 24 °C during all seasons. The outdoor evaporative coolers were able to bring the UTCI down from very strong heat stress to between thermal comfort and moderate heat stress range. These findings confirm that UTCI can be used as a reliable environmental performance metric to support the design and preservation of comfortable outdoor spaces both in a hot and a cold climate, across a variety of cultural settings. Highlights • Wi-Fi data used to study the dwelling patterns of 5,000 individuals in outdoor public spaces in Masdar Institute, Abu Dhabi. • Lunchbreak patterns of 1,200 regulars correlated with Universal Thermal Climate Index (UTCI) simulations. • The outdoor evaporative coolers are effective for thermal comfort in the hot and arid climate of Abu Dhabi. • UTCI is a reliable performance metric for the design of outdoor spaces in both a hot and a cold climate. [ABSTRACT FROM AUTHOR]

Abstract Evaporative cooling is a widely used passive cooling method to mitigate high ambient temperatures in Japan during the hot and humid summer season. An evaporative cooling louver was developed by Hirayama et al. (2014) to create a cool microclimate in an urban residential outdoor space. This study investigated the potential of using passive cooling methods integrated with the louver to create a cool microclimate in a semi-outdoor space for natural ventilation. A field measurement was conducted to evaluate the microclimate in a semi-outdoor space under different amounts of solar radiation, surrounding vegetation, and distances from louver to window to find the best way that accumulates at most the cool air generated by the louver. Best results were found when the semi-outdoor space was exposed to low solar radiation, was fully surrounded by vegetation, and when the louver was closer to the window. Moreover, to use the cool microclimate created at the semi-outdoor space for natural ventilation, different ventilation settings such as window opening area, indoor cross ventilation, and stack ventilation with a sky window were incorporated and measured to find the best conditions to induce the cool air into the indoor space. Best results were found when the window was fully open and the wind speed of the air crossing the window was more than 0.2 m/s, which maintained a cooler vertical air temperature distribution inside the window. Highlights • We found an integrated passive cooling method to form a cool microclimate at a semi-outdoor space. • The ambient temperature was reduced by 1.0–4.0 °C when passing through the evaporative cooling louver. • Cool microclimate was formed when the semi-outdoor space was surrounded by vegetation. • Formed cool air was induced into the indoor space when wind speed crossing the window was more than 0.2 m/s. [ABSTRACT FROM AUTHOR]

Abstract In this paper, experimental study of a new dehumidifier is carried out and the effects of inlet parameters of air, water and solution on the performance of the dehumidifier are discussed. The experimental results indicate that when the solution is 36 °C, the performance of the dehumidifier with outside evaporative cooling increased by 25% compared to the dehumidifier without outside evaporative cooling. The moisture removal rate is increased by a factor of 2.3 when the dehumidified air flow rate increases from 0.071 to 0.370 kg/s. Based on the experimental values, the fitting equations of enthalpy and moisture effectiveness are separately developed. The average absolute difference (AAD) of the theoretical and experimental values is less than 8% for both moisture and enthalpy effectiveness. Highlights • An experimental setup of a novel outside evaporative cooling liquid desiccant dehumidifier (OECD) was constructed. • The OECD was increased by 25% compared to NECD cooling at the solution temperature of 36 °C. • The fitting equations of the moisture and enthalpy effectiveness are developed. [ABSTRACT FROM AUTHOR]

Abstract This work deals with the probability of using a counter-flow M-cycle in Arab Gulf cities. The system is applied for weather conditions for the main cities in the region, which are Riyadh, Dammam, and Jeddah in Saudi Arabia; Abu Dhabi and Dubai in the United Arab Emirates; Kuwait, the capital of Kuwait; Doha, the capital of Qatar; and Muharraq in Bahrain. Heat and mass transfer models for the air flow in channels are developed and solved. The present model of the counter-flow M-cycle shows good agreement with the previous experimental and numerical works. The literature review shows that the critical value of ambient relative humidity is 70%. Below that value, the M-cycle could be used. This value is only exceeded sometimes in Jeddah, reaching 72.77%. The obtained results show that the supply conditions of air leaving the counter-flow M-cycle are more convenient than that can be achieved by the evaporative cooler. The M-cycle system consumes water more than the evaporative cooler. However, it uses less electrical energy than the vapor-compression refrigeration system, for the same cooling capacity. The M-cycle sometimes supplies air with conditions that do not meet the comfort condition. However, these conditions are still more convenient than those provided by the conventional evaporative cooling systems (DECs and IECs). In conclusion, the M-cycle is suitable for all selected cities and should be considered as an alternative to conventional HVAC systems in Arab Gulf Countries. Highlights • The feasibility of using a counter-flow M-cycle in Arab Gulf cities is presented. • The M-cycle is more convenient than the evaporative cooler in selected cities. • The M-cycle system uses less electrical energy than a vapor-compression system. • It is suitable to use under all weather conditions of selected cities. • It should be considered as a serious alternative to conventional HVAC systems. [ABSTRACT FROM AUTHOR]

Evaporative cooling has been considered a low energy consumption process that often is associated with displacement ventilation and passive cooling strategies of buildings. While significant energy savings can be accrued from using evaporative cooling, there are many design challenges to improve the processes of heat and mass transfer and reduce design complexities. This paper seeks to advance the design of evaporative cooling through building and testing a novel regenerative evaporative cooler prototype. It proposes a design that integrates heat pipe and porous ceramic tube modules as an alternative to plate heat exchangers. The paper describes design arrangement of the cooler, a mathematical model and laboratory test results. Under controlled laboratory test conditions, the measured performance indices of wet bulb effectiveness, specific cooling capacity and coefficient of performance (COP) were determined as 0.8, 140 W per m 2 of wet ceramic surface area and 11.43 respectively. Furthermore, experimental results show that under typical ambient conditions commensurate with that prevailing in arid climates, the cooler air supply temperature was as much as 14 °C below that of the ambient air. [ABSTRACT FROM AUTHOR]

Dry mist systems have been adopted for thermal comfort usage for some years in a temperate country like Japan. This paper seeks to study the different variables that can optimize the cooling impact from such systems. A double-flow pneumatics spray nozzle with the same pressure for air and water is used, and the experiments are conducted in a climatic chamber. Different values for wet bulb depression, pressure and water temperature are analysed, and parametric studies are conducted. The results show that wet bulb depression is a good indicator for determining operating conditions of the dry mist system, while the pressure can be varied to achieve optimal cooling at various heights on a fixed distance downstream. Changing the pressure in this study, however, had relatively small impacts on cooling due to the small change in mass flow rate. Water temperature was shown to have negligible results on cooling the air temperature at 2 m downstream, despite the variation of 10 °C. [ABSTRACT FROM AUTHOR]

Permeable pavements are effective in mitigating the urban heat island effect via evaporative cooling and have been widely used in south China. However, few studies focus on the impact of evaporative cooling of different permeable paving materials on the outdoor thermal environment. In this study, two widely used permeable paving materials, sintered ceramic porous brick (CB) and open-graded permeable concrete (PC) were investigated. First, partial immersion tests were performed to characterize the water absorption properties of these materials. The results indicated that CB had a higher water absorption rate and a larger water retaining capacity than PC. Then, field measurements were conducted to evaluate the evaporative cooling performance of these materials. The results indicated that (1) water absorption capacity has an important impact on the evaporative cooling effect of permeable materials, a high upward capillary force could maintain the hydraulic continuity over a long distance, thus effectively prolongs the first stage of evaporation, (2) sprinkling water could reduce the surface temperature of both CB and PC by up to 10 °C and lower the ratio of sensible heat flux to the net shortwave radiation of CB and PC to 13.12% and 29.62%, respectively, (3) compared to non-sprinkling conditions, the maximum air temperature above CB and PC could be decreased by up to 1 °C. Additionally, CB could lower the black globe temperature and wet-bulb globe temperature (WBGT) of 0.5 m by up to 3 °C and 2 °C after sprinkling, respectively, suggesting that sprinkling water can improve thermal comfort above pavements. [ABSTRACT FROM AUTHOR]

The potential for application of downdraught cooling in the United States of America (U.S.) depends on its climatic characteristics. However, due to the large geographic span of the country, it varies due to differences in latitude, and a range of geographic features influencing climate, including altitude, topography and terrain. This study describes the development of climatic applicability maps of downdraught cooling in the U.S., which can aid designers in the initial identification of the correct cooling strategy for the geographic area of interest. The proposed approach is based on a set of maps, which are derived from two related climatic indexes: dry bulb temperature to wet bulb temperature depression (DBT−WBT), representing the climatic opportunity, and 26 °C minus wet bulb temperature (26 °C−WBT), representing the climatic opportunity against the theoretical cooling requirement for each location. The downdraught cooling strategy and degree of applicability is classified in the map, based on the aforementioned climatic and cooling parameters. Finally, four representative buildings in four different regions with different climatic conditions were selected for climatic analysis. This resulted in the identification of some climate zones for downdraught cooling application in the U.S. and the suggestion of appropriate design strategies for each of them. [ABSTRACT FROM AUTHOR]

The Kingdom of Saudi Arabia (KSA) generates the most electricity of any country in the Gulf region, and virtually all that electricity is produced by the burning of fossil fuels - natural gas and crude oil. The residential sector accounts for about 50% of the total electricity demand in the Kingdom, and around two-thirds of that electricity consumption is used for air conditioning. As the Kingdom transitions away from its reliance on fossil fuels, reducing air conditioning energy demand in dwellings becomes a key objective. Passive cooling systems can significantly reduce cooling energy loads for buildings while maintaining thermal comfort. This study investigated the potential of integrating a passive downdraught evaporative cooling (PDEC) tower into a typical Saudi Arabian villa. A computational model of a spray PDEC tower was developed in IES-VE software and calibrated against field data. Then, an actual Saudi villa was monitored, modelled, and validated before a PDEC tower was digitally integrated into the villa. Finally, the villa and its PDEC digital twin were used to conduct a series of parametric analyses to determine the PDEC performance in different rooms and cooling energy consumption in the villa as functions of wind speed and direction. The research found that, counterintuitively, higher wind speeds reduced the effectiveness of the PDEC system to cool rooms in the villa and that wind direction also played a role in the degree of cooling experienced in different villa spaces. In the summer season, the results indicated that the total villa energy consumption was approximately 32,415 kWh in the base case, with cooling energy representing 88% of the total energy used (28,337 kWh). The integration of the PDEC tower resulted in a reduction of approximately 22% in cooling energy consumption, from 28,337 kWh to 22,032 kWh, while the PDEC was operational continuously throughout the day. • Saudi house monitored in summer; data collected via site visits & data loggers for environmental data. • Villa & PDEC tower modelled in IES-VE software, validated using building details, monitoring data. • PDEC tower virtually incorporated into villa model to assess thermal performance, wind effect & energy use. • Research found high wind speeds reduced effectiveness of PDEC system to cool rooms, wind direction played a role as well. [ABSTRACT FROM AUTHOR]

As a consequence of climate change, urban overheating has increased in all the cities of the world during the last decades. It is therefore paramount to counteract such effect by promoting the use of effective solutions to mitigate overheating at a micro-scale level. In this work, a modular experimental setup based on a water spray system was designed, realized and tested to evaluate its thermohygrometric performance in semi-outdoor spaces such as bus/train/taxi stops, street resting stations and corner shops. The setup allows to vary three operational parameters: (a) the height of the nozzles from the ground; (b) the presence of an upper shielding to reduce the impact of solar radiation; (c) the presence of a side shielding to reduce the impact of wind speed. The combination of the operational parameters allowed to evaluate the performance of five configurations for the water spray system. Several performance indexes were calculated to assess the impact of each operational parameter. It was found that the best configuration guarantees a −20% reduction of dry-bulb temperature, and the minimum specific water and electricity consumptions of the system are 0.020 L/m2 and 0.150 Wh/m2, respectively. Also, the presence of the side shielding is the parameter that mostly influences the performance of the system, followed by the height of the nozzles, while the presence of the upper shielding has a minor effect. These operational parameters, however, increase relative humidity inside the nebulization volume; it is therefore important to verify if undesired wet conditions are reached. • A modular water spray system is designed, realized and tested. • Three operational parameters and five configurations are evaluated. • The best configuration guarantees a −20% reduction of dry-bulb temperature. • The minimum specific water and electricity consumptions are 0.020 L/m2 and 0.150 Wh/m2. • The presence of the side shielding mostly influences the performance of the system. [ABSTRACT FROM AUTHOR]

Despite the fact that wet-membrane humidifiers are commonly used, their designs and forecasts of humid air are generally based on very simple experimental data, which has resulted in certain design errors. Though some numerical models have been developed in the literature, these models make some idealized assumptions about the fluid flow inside the wet-membrane medium in order to solve the momentum conservation equation. Besides, these models had not been validated using accurate experimental data. Thus, based on a thorough examination of the physical procedure of wet-membrane humidification, a new numerical model for the wet-membrane humidification process is developed that can precisely predict the outlet air temperature and Relative Humidity (RH) under a variety of conditions. To verify the model's correctness, the authors built a wet-membrane humidification test-bed and carried out orthogonal experiments with various inlet factors. The numerical model was validated using the experimental data, and it was then utilized to compare various humidifier design strategies. It is found that the ability of the wet-membrane humidifier to humidify the air under the same heat gain increases when the inlet water is heated rather than the inlet air. While using this method, the inlet water parameters and wet-membrane size must be properly set in order to prevent humid air supersaturation. • A new numerical model for the wet-membrane humidification process was developed. • The model's correctness was verified by orthogonal experiments with various inlet factors. • As a design strategy to enhance humidification capacity, heating the inlet water has good development potential. • Problems with conventional design methods under non-adiabatic conditions are discussed. [ABSTRACT FROM AUTHOR]

Liquid desiccant evaporative cooling air-conditioning (LDECAC) system, which combines both advantages of liquid desiccant and evaporative cooling technology, has a great potential to utilize low-grade heat for refrigeration and air conditioning. A novel LDECAC system is proposed to obtain lower supply air temperature and humidity ratio at the expense of less thermal energy consumption when used as a dedicated fresh air system. It consists of a liquid desiccant system with self-cycle solution at dehumidification and regeneration sides, a regenerative indirect evaporative cooler (RIDEC) and a direct evaporative cooler with adjustable by-pass flow. A parametric study on steady-state thermal performance of LDECAC system was performed based on the developed mathematical model. The performance was investigated by varying five key parameters: solution self-cycle ratio ( R s ), working to intake air flow ratio ( R a ), regeneration temperature, ambient air temperature and humidity ratio. The results show that the system can handle the process air to 17.9 °C and 9.2 g/kg with the thermal coefficient of performance of 0.56 under the design condition. The recommended value for R s lies between 0.6 and 0.7 and that for R a is 0.2 under the typical operating condition. The variable R s control method is effective in response to the change of ambient air conditions. Performance comparison with the conventional LDECAC system shows that the novel system can utilize lower temperature heat source and achieve a higher thermal coefficient of performance. [ABSTRACT FROM AUTHOR]

The characteristic that describes the extent to which buildings and their systems maintain their performance during shocks is called resilience. Building policies in the EU have already addressed the resilience of buildings against possible hazards (i.e., natural disasters, extreme weathers, fires). However, with increasing overheating risks (e.g., climate change) accompanied by their detrimental health and economic impacts, the thermal performance of nearly zero energy buildings (nZEB) is not guaranteed. This study aims to assess the impact of shocks and combinations on the thermal resilience of educational nZEB against heatwaves (HW) and system shocks (SS) including failure of indirect evaporative cooling (IEC), natural night ventilation (NNV) and solar shading failure (SF). A Modelica model of the building was developed and experimentally validated. Shocks were classified and quantified using the novel normalized degree of shock (d o S) index. Heatwaves (HWs) had 20 × to 93 × more critical impact than the worst SS (NNV failure). Additionally SS occurring at the start of the operational period is 1.2 × more critical than SS occurring later in the day as it allowed for significant heat build-up in both classrooms. In future climate scenarios a combination of HWs and power outages will become frequent. This study showed that a combination of a full day of cooling strategy and shading failure occurring on the hottest day of a 6-day long HW , is 10% more critical on both lecture rooms than an individual 10-day long HW. Classroom with heavy thermal mass prolongs the absorptivity of the shocks but delays recovery. [Display omitted] • Impact of external & system shocks on resilience to overheating of educational nZEB. • External & system shocks (SS) quantified with the novel normalized degree of shock. • Heatwaves (HW) are 20–93 × more critical than IEC, NNV & shading failure. • System shock at the start of operation is 1.2× more critical than later in the day. • Combined 6 day HW & SS is 10% more critical than a single 10 day HW. [ABSTRACT FROM AUTHOR]

Greenhouse overheating is a major problem for dry climate agricultural setups during the summer months. Evaporative cooling is a convenient solution for controlling indoor temperature on hot and dry days. However, conventional evaporative cooling pad materials such as polymers, cellulose, and organic fibres present problems in terms of high carbon footprint, after-use disposal, and/or very limited lifespan. In this study, porous concrete was tested as a novel evaporative cooling pad material in an experimental wind tunnel with different inlet air temperatures at a constant air velocity (2.5 m s−1). The porous concrete evaporative cooling pad demonstrated the highest evaporative cooling capacity at −11.46 kW sensible cooling with 10.17 kW m−2 °C−1 cooling coefficient. It further exhibited an evaporation rate of 5.84 g s−1 with an evaporation coefficient of 1.56 m s−1. The average cooling effectiveness was obtained as 0.97, where some inlet air conditions demonstrated negative enthalpy changes after evaporation. However, the maximum average enthalpy change was 10.97 kJ kg−1. This novel evaporative cooling pad material showed the highest effectiveness when compared to conventional evaporative cooling pad systems reported in other studies. • Porous concrete is a prospective new evaporative cooling pad (ECP) material. • A high cooling capacity (10.2 kW m−2 °C−1 heat transfer coefficient) was obtained. • Cooling effectiveness reached 1.00 for inlet air temperatures ranging from 30 to 40 °C. • The average cooling effectiveness was 0.97. • Enthalpy changes showed (−)ve values with low inlet temperatures (30–40 °C). [ABSTRACT FROM AUTHOR]

Indirect evaporative cooling, by using water evaporation to absorb heat to lower the air temperature without adding moisture, is an extremely low energy and environmentally friendly cooling principle. The properties of the wet channel surface in an indirect evaporating cooler, i.e. its moisture wicking ability, diffusivity and evaporation ability, can greatly affect cooling efficiency and performance. Irregular fibres help to divert moisture and enlarge the wetted area, thus promoting evaporation. A range of fabrics (textiles) weaved from various fibres were experimentally tested and compared to Kraft paper, which has been conventionally used as a wet surface medium in evaporative coolers. It was found that most of the textile fabrics have superior properties in moisture wicking ability, diffusivity and evaporation ability. Compared with Kraft paper, the wicking ability of some fabrics was found to be 171%–182% higher, the diffusion ability 298%–396% higher and evaporation ability 77%–93% higher. A general assessment concerning both the moisture transfer and mechanical properties found that two of the fabrics were most suitable for indirective evaporative cooling applications. [ABSTRACT FROM AUTHOR]

Indirect Evaporative Cooling Systems (IECS), characterized by the use of wetted roof or wall surfaces for structural cooling without increasing indoor air humidity, consist of an interesting bioclimatic strategy still not quite explored in Brazil. This study aims to evaluate the thermal performance of an IECS by means of experiments with test cells in a subtropical location. Experiments were carried out for Curitiba, Brazil (25.5ºS, 49ºW, 910 a.m.s.l.) with two equal-sized small test cells, first with a control cell without the roof pond and with each test cell fitted with roof ponds, for testing different modes of operation of the IECS. Configurations of the system encompassed: a) conventional roof pond-based IECS; b) roof pond with sealed water reservoir, naturally ventilated and fully shaded (for testing the effect of thermal mass without the evaporative function); c) IECS with an unshaded roof pond. The relative contributions of evaporation and shading have been assessed. The year-round evaluation showed a high cooling performance of the IECS for the subtropical location tested. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the operational performance and impact factors of a counter-flow regenerative evaporative cooler (REC). This was undertaken through a dedicated experimental process. Temperature, humidity and flow rate of the air flows at the inlet, outlet and exhaust opening of the cooler were tested under various operational conditions, i.e., different inlet air conditions, feed water temperature and evaporation rate were also correspondingly measured. It was found that the wet-bulb effectiveness of the presented cooler ranged from 0.55 to 1.06 with Energy Efficiency Ratio (EER) rated from 2.8 to 15.5. The major experimental results were summarised below: 1) the wet-bulb effectiveness was significantly enhanced through either ways of increasing inlet wet-bulb depression or reducing intake air velocity, or alternatively by increasing working-to-intake air ratio; 2) the cooling capacity and EER of cooler was rapidly increased by means of increasing inlet wet-bulb depression or increasing intake air velocity, or reducing working-to-intake air ratio instead; 3) the effectiveness reduced by less 5% while feed water temperature increased from 18.9 to 23.1 °C; 4) apparent acceleration in water evaporation rate was gained from increasing inlet wet-bulb depression or air velocity. The presented cooler showed 31% increase in wet-bulb effectiveness and 40% growth in EER compared to conventional indirect evaporative cooler. The research helped identifying the performance of a new REC with enhanced performance and thus contributed to development of energy efficient air conditioning technologies, which eventually lead to significant energy saving and carbon emissions reduction in air conditioning sector. [ABSTRACT FROM AUTHOR]

This research paper investigates the use of vertical gardens as evaporative coolers. Vertical gardens play a key role in tackling the increasing challenges cities face, due to a rapidly growing urban environment with associated reductions in vegetation and an increase in the urban heat island effect. This paper aims to develop a mathematical model based on the FAO-56 Penman Monteith Equation that quantifies the effects of vertical gardens for evaporative cooling. The theoretical results are then compared with empirical findings for the experimental setup undertaken by Davis & Ramirez [1], which involved passing air behind the vertical garden (between the substrate and the surface). Correlation is observed when the computed value is at the lowest humidity (35%) of the three test runs (35%, 40%, and 45%). This either indicates that the vertical garden performs better than predicted by the mathematical model, or the relative humidity at the time when the measurements were made was in the region of 35% instead of the predicted 40%. This research indicates the potential for the FAO-56 Penman Monteith Equation to be integrated into a future design tool that facilitates the application of vertical gardens as evaporative coolers in building designs. [ABSTRACT FROM AUTHOR]

Evaporative cooling by water spray is increasingly used as an efficient and environmentally-friendly approach to enhance thermal comfort in built environments. The complex two-phase flow in a water spray system is influenced by many factors such as continuous phase velocity, temperature and relative humidity patterns, droplet characteristics and continuous phase–droplet and droplet–droplet interactions. Computational Fluid Dynamics (CFD) can be a valuable tool for assessing the potential and performance of evaporative cooling by water spray systems in outdoor and indoor urban environments. This paper presents a systematic evaluation of the Lagrangian–Eulerian approach for evaporative cooling provided by the use of a water spray system with a hollow-cone nozzle configuration. The evaluation is based on grid-sensitivity analysis and validated using wind-tunnel measurements. This paper also presents a sensitivity analysis focused on the impact of the turbulence model for the continuous phase, the drag coefficient model, the number of particle streams for the discrete phase and the nozzle spray angle. The results show that CFD simulation of evaporation by the Lagrangian–Eulerian (3D steady RANS) approach, in spite of its limitations, can accurately predict the evaporation process, with local deviations from the wind-tunnel measurements within 10% for dry bulb temperature, 5% for wet bulb temperature and 7% for the specific enthalpy. The average deviations for all three variables are less than 3% in absolute values. The results of this paper are intended to support future CFD studies of evaporative cooling by water spray systems in outdoor and indoor urban environments. [ABSTRACT FROM AUTHOR]

Reliable estimates of evaporative water loss are required to assess the urban water budget in support of division of water resources among various needs, including heat mitigation measures in cities relying on evaporative cooling. We report on urban evaporative water loss from Arnhem and Rotterdam in the Netherlands, using eddy covariance, scintillometer and sapflow observations. Evaporation is assessed at daily to seasonal and annual timescale. For the summer half-year (April–September), observations from Arnhem and Rotterdam are consistent regarding magnitude and variability of evaporation that typically varies between 0.5 and 1.0 mm of evaporation per day. The mean daily evaporative cooling rate was 20–25 Wm −2 , 11–14% of the average incoming solar radiation. Evaporation by trees related to sapflow was found to be a small term on the water budget at the city or neighbourhood scale. However, locally the contribution may be significant, given observed maxima of daily sap flows up to 170 l per tree. In Arnhem, evaporation is strongly linked with precipitation, possibly owing to building style. During the summer season, 60% of the precipitation evaporated again. In Rotterdam, the link between evaporation and precipitation is much weaker. An analysis of meteorological observations shows that estimation of urban evaporation from routine weather data using the concept of reference evaporation would be a particularly challenging task. City-scale evaporation may not scale with reference evaporation and the urban fabric results in strong microweather variability. Observations like the ones presented here can be used to evaluate and improve methods for routine urban evaporation estimates. [ABSTRACT FROM AUTHOR]

In dry and cold climates, a cool mist humidifier and a floor heating system are typically used in combination to achieve a pleasant residential environment. In order to investigate the interaction between a humidification process and a heating process, a total of 12 experimental tests were carried out, which included nine experimental groups with a humidification process under the conditions of three indoor temperature set points (21 °C, 23 °C, 25 °C) and three relative humidity set points (45%, 55%, 65%), and three control groups with no humidification process under the conditions of three indoor temperature set points (21 °C, 23 °C, 25 °C). Obtained results show that the indoor environment will reach a new balance in the process of competition between the evaporative cooling and the floor heating, and the floor surface temperature increases when the humidification level rises. The floor overheating problem should be considered while meeting humidification needs at air temperatures of 25 °C or above. The humidification process makes the air temperature distribution more uniform, but increases the energy consumption noticeably. In addition, exergy loss is mainly concentrated in two areas: the building envelope and the floor for the floor heating system. In summary, the set point of RH 45% could meet general health requirements in the case of minimal energy consumption. RH 55% could be selected at below 25 °C for better thermal comfort in particular situations where the energy consumption is acceptable. • Interaction of a cool mist humidifier and a floor heating system was investigated. • Floor surface temperature increases with the humidification level rising. • Floor overheating problem should be considered at air temperatures of 25° or higher. • Humidification process makes the air temperature distribution more uniform. • Exergy loss is mainly concentrated in the building envelope and the floor. [ABSTRACT FROM AUTHOR]

Extensive green roof system is widely used due to its lightweight, thin growing media, limited or no maintenance, low cost, and high potential application for use over the new or existing lightweight structures. This study is focused on the energy performance and rainwater retention performance of extensive green roofs when coupled with highly insulated roof deck. In this experimental study, three roof systems: conventional roof (CR) and two extensive green roofs with plants (GR) and with no plants (GM) are constructed, instrumented and their responses to real environmental conditions are monitored for over a year and analyzed. The experimental results suggest that during wet period, the rainwater retention potential of green roof is only about 21%, while in the summer the rainwater retention capacity increases as high as 100%. Plants play an important role in rainwater interception, growing media wetness, rain runoff and the green roof's thermal performance by modifying short- and long-wave radiation and as well as convective heat exchanges. Installation of green roofs on highly insulated roof decks yields a mixed performance in a mild and wet climate. The heat loss through the green roof during the heating months is about 2% higher than a similar roof without green roof. Whereas during the cooling months the green roof is able to reduce the heat gain by 66%. This substantial heat gain reduction can help to reduce overheating problems in highly insulated buildings. • Green roof installed on a highly insulated roof has marginal winter performance. • Green roof systems in the summer help to shave and shift peak cooling load. • In cold climate green roof keeps roof sheathing warm and reduce condensation risk. • Plants have impacts on both rainwater retention and roof thermal performance. • Evaporative cooling plays a significant role in lowering buildings' heat gain. [ABSTRACT FROM AUTHOR]

Falling film heat and mass transfer, representatives of advanced and low-carbon heat and mass transfer technologies, has been applied in a variety of thermal processes due to its great prospect for heat and mass transfer enhancement. However, the hydrodynamics, heat and mass transfer are significantly influenced by the gas (vapor or air) streams during the operation of falling film heat exchangers. To acquire the detailed profiles of flow, temperature and concentration and to explore the influence mechanism of gas stream shearing on the falling film hydrodynamics and heat and mass transfer, researchers have adopted experimental, analytical and numerical methods for different attempts. This paper presents a comprehensive summarization of the relevant work concerning the hydrodynamic, heat and mass transfer characteristics of falling film components, including the evaporator, absorber, evaporative cooler and dehumidifier. Considering the specific applications, the cocurrent, countercurrent, and cross gas streams shearing on the liquid film on a horizontal tube and bundle, a vertical tube and a vertical plate are reviewed. The objective of this review is to cover sufficient knowledge of the results, findings and insights of gas stream impacts on the hydrodynamics, heat and mass transfer in building utilized heat exchangers to provide guidance on how to maximize the positive effect or at least minimize the negative impact of gas shearing on the falling film heat and mass transfer. Schematics of gas stream models encountered in various applications. [Display omitted] • Provide the first review of the gas stream effect on falling liquid film flow. • Clarified mechanisms of gas effect on liquid film flow, heat and mass transfer. • Summarized studies of gas stream effect on falling film flow, heat and mass transfer. • Concerned film thickness, heat and mass transfer prediction under gas shearing. • Proposed some recommendations and improvements for future research. [ABSTRACT FROM AUTHOR]

Abstract: In warm environments, room fans can provide comfort using substantially less energy than air-conditioning. The savings are greater if the fans make it possible to successfully condition the building with natural ventilation or evaporative cooling systems, instead of chillers. Although there are many laboratory studies of comfort using desk fans and personalized fans, tests for ceiling fans are rare, mainly in early studies from the 1980s. This study examines the cooling effect of a low-wattage ceiling fan on occupants when air comes from different directions with different speeds. We conducted 96 human subject tests in an environmental chamber. Sixteen college students each experienced 6 air movement conditions: two different air speeds and three different air directions between fan and subject: from front, side, or right above the head (total eleven configurations). The difference in thermal comfort and thermal sensation generated by fixed and oscillating fans was also investigated. The temperature and humidity conditions for the tests were 28 °C and 50% RH. It was found that the majority of subject (70%) perceive the thermal environment without fans comfortable. This number rise to 100% for some configuration with fans. Our subject found that the oscillating air movement had no effect in terms of improved thermal comfort or thermal sensation, but it greatly improves their air quality perception. The subjects did not report any dry eyes discomfort for any of the eleven configurations. [Copyright &y& Elsevier]

Abstract: With the rapid intensification of urban heat islands worldwide, measures for its mitigation are gaining attention. Some of the most popular measures are based on employing evaporative cooling, altering the surfaces' albedo or making use of shading. In this paper, we numerically investigate the influence of each of these three methods on the comfort of a pedestrian in a typical urban street canyon. The environmental conditions in the urban street canyon are obtained from a detailed microclimatic model, and serve as input for a comfort model based on the Universal Thermal Climate Index (UTCI). Simulations are conducted for average summer conditions, taken from a typical meteorological year (TMY), and for heat wave (HW) conditions. The results show that evaporative cooling can considerably reduce the air temperature and the mean radiant temperature, but that the corresponding increase in vapor pressure limits the net gain in comfort. Shading results in significantly reduced surface temperatures, in addition to decreasing the intensity of direct solar irradiation, both leading to an increased comfort sensation. Increasing the local albedo of urban surfaces also leads to lower surface temperatures, but does not affect the amount of direct solar irradiation, explaining the lower comfort gain compared to shading. The cooling effect of all methods proved to increase during a HW in comparison to a TMY. These observations show that the effectiveness of mitigation measures highly depends on the climatic conditions and demonstrate the potential of microclimatic models to determine the optimal combination of measures for a given context. [Copyright &y& Elsevier]

Heating, ventilation, and air conditioning (HVAC) systems for large buildings often use water for cooling. The U.S. Department of Defense funded the demonstration of a novel hygroscopic HVAC cooling tower technology with the goal of reducing water usage. We quantified direct and indirect water usage and greenhouse gas (GHG) emissions to analyze the tradeoffs associated with transitioning from a conventional wet-cooling HVAC tower to the hygroscopic system. We quantified GHG emissions for electricity consumed directly by the building-scale cooling system and the indirect electricity associated with water and wastewater conveyance and treatment. We found that the GHG emissions impact of increased electricity consumption in the building-scale cooling system is greater than the GHG emissions impact of indirect energy savings from the decrease in water usage, resulting in a net increase in GHG emissions. The indirect water consumption associated with cooling water for electricity generation was comparatively low when compared to direct water usage volumes that were reduced by switching to the hygroscopic system. The hygroscopic system showed promising water savings ability that is best suited to regions with extreme water scarcity, high water sourcing and treatment energy intensity, and/or when the electricity is sourced from low-carbon sources. • Hygroscopic cooling towers are an alternative to evaporative cooling. • The hygroscopic technology effectively reduced water requirements. • Additional operational electricity increases net greenhouse gas emissions. • Tradeoffs exist between water usage and emissions for building cooling towers. • Hygroscopic systems are suitable for arid areas and low-carbon electricity. [ABSTRACT FROM AUTHOR]

Pervious pavement is an efficient cooling strategy to alleviate the urban heat island (UHI) effect because it can retain percolating rainwater for subsequent evaporative cooling. The cooling effect simulation of pervious pavement before implementation is necessary to understand its contribution to the thermal environment. However, it still confronts challenges, due to limited estimation methods of evaporation rate. In this study, we proposed an approach to simulate the evaporation rate of pervious pavements by using the evaporation resistance method (ERM). First, the exponential relationship between evaporative resistance and volumetric water content of two widely used pervious paving materials was regressed by wind tunnel experiments. Second, this ERM was validated by outdoor field experiments of pervious pavements after being integrated into a heat transfer model. Lastly, the best water-sprinkling time was determined based on the model. The results revealed that the evaporation resistance sharply increased when the volume water content of ceramic brick (CB) and pervious concrete (PC) was below 6.5% and 11.8%, respectively. The regressed relationships revealed a high accuracy with all R2 above 0.85, and the root mean square error of the surface temperature of the pervious pavement between measurement and simulation demonstrated a high accuracy with CB of 1.31 °C and PC of 1.64 °C. Sprinkling during 07:00 to 11:00 under typical hot-humid climate summer days could gain a win-win effect with sizeable evaporation cooling effects and water-saving. • We proposed an ERM model for evaporation estimation of pervious pavements. • Evaporative resistance of pervious materials was regressed by wind tunnel experiments. • The ERM model was adopted to simulate the temperature evolution of pervious pavement system. • Sprinkling during 07:00–11:00 in summer days would be the best practice to re-wet pervious pavements. [ABSTRACT FROM AUTHOR]

Abstract: Total electricity and water burdens, including both direct and indirect uses, were modeled for newly constructed and 15-year-old homes in six California climate zones for three air conditioning systems: standard air-cooled condensing unit, evaporatively pre-cooled condensing unit, and an evaporative condensing unit. Compared to the air-cooled condensing unit, average annual direct electricity savings were 17.7% and 11.3% for an evaporatively pre-cooled condensing unit and an evaporative condensing unit, respectively. The evaporative condensing unit provided greater savings at peak load than the evaporatively pre-cooled condensing units (peak power savings were 30.9% and 23.8%, respectively), which is promising for hot arid climates. Total water burden reflected direct (e.g., evaporation) and indirect (i.e., electricity generation) water use. The standard air-cooled condensing unit, which had only an indirect water burden, exhibited the lowest total water burden; the evaporatively pre-cooled condensing unit and evaporative condensing unit had similar total water burdens, which were approximately double the air-cooled condensing unit's total water burden. This is because the evaporatively pre-cooled condensing unit and evaporative condensing unit both required a substantial volume of water (average 30.8 and 28.1 L/h, respectively; up to 8.5% increased water consumption for a typical household) to achieve their electricity-saving and peak power reduction benefits. This additional water burden can be offset by implementing an in-home decentralized graywater treatment and reuse plan, where shower and clothes-wash water is treated and recycled in-home for evaporative cooling as well as irrigation and toilet flushing. [Copyright &y& Elsevier]

Abstract: Recent activity in the development of future weather data for building performance simulation follows recognition of the limitations of traditional methods, which have been based on a stationary (observed) climate. In the UK, such developments have followed on from the availability of regional climate models as delivered in UKCIP02 and recently the probabilistic projections released under UKCP09. One major area of concern is the future performance and adaptability of buildings which employ exclusively passive or low-energy cooling systems. One such method which can be employed in an integral or retrofit situation is direct or indirect evaporative cooling. The effectiveness of evaporative cooling is most strongly influenced by the wet-bulb depression of the ambient air, hence is generally regarded as most suited to hot, dry climates. However, this technology has been shown to be effective in the UK, primarily in mixed-mode buildings or as a retrofit to industrial/commercial applications. Climate projections for the UK generally indicate an increase in the summer wet-bulb depression, suggesting an enhanced potential for the application of evaporative cooling. The paper illustrates this potential by an analysis of the probabilistic scenarios released under UKCP09, together with a detailed building/plant simulation of case study building located in the South-East of England. The results indicate a high probability that evaporative cooling will still be a viable low-energy technique in the 2050s. [Copyright &y& Elsevier]

Abstract: In this paper, a low-speed wind tunnel was used for experimental analysis of water volume retained, pressure drop, saturation efficiency and water consumption for three types of synthetic substrates used in active living walls: polyester (PR), polyurethane (PU) and polyamide–polypropylene (PA–PP) The substrates were of a similar thickness and were tested for different water and air flows. The water retained increases with higher water flow. The pressure drop increases with the presence of vegetation and when air speed and water flow is higher. Cooling efficiency is enhanced with vegetation and low air speed. Specific consumption of water is greater with vegetation at higher air speeds. Therefore, low air (between 0.25 and 0.5 m s−1) and water flows are recommended to ensure a homogeneous wetting of the substrate surface. PA–PP has the greatest pressure drop of the three, but also presents the best saturation efficiency, with an average water retention capacity and less specific consumption. PU offers the least resistance to air flow, with an intermediate efficiency level and high water consumption and water retention capacity. PR presents the worst saturation efficiency, a medium level of pressure drop and high water consumption. [Copyright &y& Elsevier]

Abstract: In this paper, numerical analyses of the thermal performance of an indirect evaporative air cooler incorporating a M-cycle cross-flow heat exchanger has been carried out. The numerical model was established from solving the coupled governing equations for heat and mass transfer between the product and working air, using the finite-element method. The model was developed using the EES (Engineering Equation Solver) environment and validated by published experimental data. Correlation between the cooling (wet-bulb) effectiveness, system COP and a number of air flow/exchanger parameters was developed. It is found that lower channel air velocity, lower inlet air relative humidity, and higher working-to-product air ratio yielded higher cooling effectiveness. The recommended average air velocities in dry and wet channels should not be greater than 1.77m/s and 0.7m/s, respectively. The optimum flow ratio of working-to-product air for this cooler is 50%. The channel geometric sizes, i.e. channel length and height, also impose significant impact to system performance. Longer channel length and smaller channel height contribute to increase of the system cooling effectiveness but lead to reduced system COP. The recommend channel height is 4mm and the dimensionless channel length, i.e., ratio of the channel length to height, should be in the range 100 to 300. Numerical study results indicated that this new type of M-cycle heat and mass exchanger can achieve 16.7% higher cooling effectiveness compared with the conventional cross-flow heat and mass exchanger for the indirect evaporative cooler. The model of this kind is new and not yet reported in literatures. The results of the study help with design and performance analyses of such a new type of indirect evaporative air cooler, and in further, help increasing market rating of the technology within building air conditioning sector, which is currently dominated by the conventional compression refrigeration technology. [ABSTRACT FROM AUTHOR]

Abstract: As a passive cooling strategy to control increased surface temperatures and create cooler urban environments, we have developed a passive evaporative cooling wall (PECW) constructed of pipe-shaped ceramics that possess a capillary force to absorb water up to a level higher than 130 cm. The current paper presents a simulation system to predict and evaluate microclimatic modifying effects of PECWs in urban locations where PECW installation is under consideration at the design stage. This simulation system is composed of a CFD simulation tool and a 3D-CAD-based thermal simulation tool. Simulation methodology of coupling the two simulation tools was developed and described in this paper. Numerical models for simulating surface temperatures and evaporation of PECWs were proposed based on analysis results of experimental data. Validation of the proposed numerical models was confirmed by comparing simulated results with measured data. In order to demonstrate the applicability of the proposed simulation system, a case study was then performed to predict and evaluate the microclimate in a rest station where PECWs were assumed to be installed. Spatial distributions of air temperature, airflow, moisture and surface temperature in the rest station were simulated under a sunny weather condition in the summer of Tokyo. Furthermore, thermal comfort indexes (mean radiant temperature and new standard effective temperature) were used to evaluate thermal comfort in the human activity spaces of the rest station. Simulation results show that this simulation system can provide quantitative predictions and evaluations of microclimatic modifying effects resulting from the application of PECWs. [ABSTRACT FROM AUTHOR]

Abstract: Aimed at controlling the increase in urban surface temperature and creating comfortable urban environments in summer, the authors have developed a passive evaporative cooling wall (PECW) constructed of porous ceramics. These ceramics enable their vertical surfaces to be wet up to a level higher than 100 cm when their lower end is placed in water. Our previous study has demonstrated the cooling performance and applicability of a prototype PECW constructed of pipe-shaped ceramics (ceramic pipes). The present paper presents a PECW unit system which can be easily installed for practical applications. Experiments were conducted using experimental PECW units. Experimental results show that the ceramic pipe developed in this study possessed a higher water-holding and soaking-up ability than the previous one. Wet surfaces of the new ceramic pipe reached a height of over 130 cm at an outdoor location exposed to solar radiation on sunny summer days. Furthermore, the air passing through the PECW unit was cooled, and its temperature can be reduced by around 2 °C during summer daytime. These results indicate that the proposed PECW can be broadly applied to various urban locations. [ABSTRACT FROM AUTHOR]

Abstract: Singapore experiences a hot and humid climate throughout the year. This in turn results in heavy reliance on mechanical systems especially air-conditioning to achieve thermal comfort. An alternative would be the use of evaporative cooling which is less energy intensive. Objective and subjective measurements were conducted at an experimental setup at the National University of Singapore (NUS) to evaluate the thermal conditions and thermal sensations brought about by misting fans. Field measurements were also conducted at food centres in Singapore to determine if they are coherent with the objective and subjective measurements conducted. Analysis of objective and subjective data showed that the misting fan was able to significantly reduce the dry-bulb temperature and thermal sensation votes. This is consistent with field measurements taken, where regression analysis showed that with the misting fan, thermal neutrality can be obtained at a higher outdoor effective temperature (ET*). However, the reduction in temperature comes at the expense of higher relative humidity which results in consistently greater biological (bacterial and fungal) pollutants being enumerated from samples collected under the misting fan system. In some samples, the bacteria count is very much greater than samples collected under the non-misting fan, illustrating the potential for a substantial increase in biological pollutants due to the generation of mists. [ABSTRACT FROM AUTHOR]

Abstract: Existing desiccant cooling systems reduce the temperature of process air either by adopting evaporative coolers or incorporating vapor compression systems. While the former is restricted by inaccurate control, the latter still consumes certain quantity of electric power. To solve this problem, a thermally driven air conditioning system, which combines the technologies of rotary desiccant dehumidification and regenerative evaporative cooling, has been proposed and investigated. In addition to dehumidification, the system is capable of producing chilled water, thereby realizing separate temperature and humidity control without increasing electrical load. To find out the characteristics of produced chilled water and evaluate the feasibility and energy saving potential of this novel system, a mathematical model has been developed. Case studies have been conducted under Air conditioning and Refrigeration Institute (ARI) summer, ARI humid and Shanghai summer conditions. It is found that the system can achieve a thermal COP higher than 1.0 and an electric COP about 8.0. The temperature of chilled water produced by the system is around 14–20 °C. This chilled water can be used with capillary tube mats for radiant cooling. It is suggested that the system can also be designed as a standalone chilled water plant. As a desiccant dehumidification-based chilled water producing technology, this would expand desiccant cooling to a boarder niche application. The effects of chilled water flow rate, air distribution ratio, inlet air conditions and regeneration temperature have been analyzed in detail. Reachable handling regions, which will be helpful to system design and optimization, have been obtained. [Copyright &y& Elsevier]

Abstract: In this paper, the results of performance analysis of a ground-assisted hybrid evaporative cooling system in Tehran have been discussed. A Ground Coupled Circuit (GCC) provides the necessary pre-cooling effects, enabling a Direct Evaporative Cooler (DEC) that cools the air even below its wet-bulb temperature. The GCC includes four vertical ground heat exchangers (GHE) which were arrayed in series configuration. In order to have an accurate prediction of the optimum performance of a GCC, a computational fluid dynamic simulation was performed. Simulation results revealed that the combination of GCC and DEC system could provide comfort condition whereas DEC alone did not. Based on the simulation results the cooling effectiveness of a hybrid system is more than 100%. Thus, this novel hybrid system could decrease the air temperature below the ambient wet-bulb temperature. This environmentally clean and energy efficient system can be considered as an alternative to the mechanical vapor compression systems. [Copyright &y& Elsevier]

Abstract: In this paper, the results of a study on a hybrid system of nocturnal radiative cooling, cooling coil, and direct evaporative cooling in Tehran have been discussed. During a night, the nocturnal radiative cooling provides required chilled water for a cooling coil unit. The cold water is stored in a storage tank. During eight working hours of the next day, hot outdoor air is pre-cooled by means of the cooling coil unit and then it enters a direct evaporative cooling unit. In this period, temperature variation of the conditioned air is investigated. This hybrid system complements direct evaporative cooling as if it consumes low energy to provide cold water and is able to fulfill the comfort condition whereas direct evaporative alone is not able to provide summer comfort condition. The results obtained demonstrate that overall effectiveness of hybrid system is more than 100%. Thus, this environmentally clean and energy efficient system can be considered as an alternative to the mechanical vapor compression systems. [Copyright &y& Elsevier]

Abstract: In this paper, we compare results of a long-term temperature monitoring in a building with high thermal mass to indoor temperature predictions of a second building that uses an indirect evaporative cooling system as a means of passive cooling (Vivienda Bioclimática Prototipo -VBP-1), for the climatic conditions of Sde Boqer, Negev region of Israel (local latitude 30°52′N, longitude 34°46′E, approximately 480m above sea level). The high-mass building was monitored from January through September 2006 and belongs to a student dormitory complex located at the Sde Boqer Campus of Ben-Gurion University. VBP-1 was designed and built in Maracaibo, Venezuela (latitude 10°34′N, longitude 71°44′W, elevation 66m above sea level) and had its indoor air temperatures, below and above a shaded roof pond, as well as the pond temperature monitored from February to September 2006. Formulas were developed for the VBP-1, based on part of the whole monitoring period, which represent the measured daily indoor maximum, average and minimum temperatures. The formulas were then validated against measurements taken independently in different time periods. The developed formulas were here used for estimating the building''s thermal and energy performance at the climate of Sde Boqer, allowing a comparison of two different strategies: indirect evaporative cooling and the use of thermal mass. [Copyright &y& Elsevier]

Abstract: As a passive cooling strategy aimed at controlling increased surface temperatures and creating cooler urban environments in summer, the authors developed a passive evaporative cooling wall (PECW) constructed of porous ceramics. These ceramics possess a capillary force to soak water, which means that their vertical surface is wet up to a level higher than 100cm when their lower end is placed in water. The present paper describes an experiment that clarifies the cooling effects of a prototype PECW constructed of pipe-shaped ceramics. The PECW is capable of absorbing water and allows wind penetration, thus reducing its surface temperature by means of water evaporation. Passive cooling effects such as solar shading, radiation cooling, and ventilation cooling can be enhanced by incorporating PECWs into the design of outdoor or semi-outdoor spaces in parks, pedestrian areas and residential courtyards. The following findings were understood from an experimental data collected over a summer period. Wet vertical surfaces of the ceramic pipe reached a height of over 1m at an outdoor location exposed to solar radiation. Wet surface conditions can be maintained throughout successive sunny days during summer. A slight difference in the vertical surface temperatures of the ceramic pipe was found. The air passing through the PECW was cooled, and its temperature can be reduced to a minimum value by several degrees during summer daytime. It was also found that the surface temperature of the shaded ceramic pipe can be maintained at a temperature nearly equal to the wet-bulb temperature of outdoor air. [Copyright &y& Elsevier]

Abstract: Shanghai as the largest city in China has been suffering from the ever-worsening thermal environment due to the explosive urbanization rate. As an indication of urbanization impact, urban heat islands (UHI) can give rise to a variety of problems. This paper reports the results of an empirical study on the summertime UHI patterns in three high-rise residential quarters in the inner-city Shanghai. Site-means of UHI intensity are compared; case studies are carried out on strategically located measurement points; and regression analysis is followed to examine the significance of the on-site design variables in relation to UHI intensity. It is found that site characteristics in plot layout, density and greenery have different impacts on UHI-day and UHI-night patterns. Day-time UHI is closely related to site shading factor. Total site factor (TSF) as an integrated measure on solar admittance shows a higher explanatory power in UHI-day than sky view factor (SVF) does under a partially cloudy sky condition. Night-time UHI cannot be statistically well explained by the on-site variables in use, indicating influences from anthropogenic heat and other sources. Evaporative cooling by vegetation plays a more important role at night than it does at day. Considered diurnally, the semi-enclosed plot layout with a fairly high density and tree cover has the best outdoor thermal condition. Design implication based on the findings, with consideration on other important environmental design issues, is briefly discussed. [Copyright &y& Elsevier]

Abstract: Packed-bed heat and mass transfer devices are widely used in air-conditioning systems, such as cooling tower, evaporative cooler of air–water direct-contact devices, dehumidifier and regenerator of air–liquid desiccant direct-contact devices. Similarities of heat and mass transfer characteristics between air–water and air–liquid desiccant devices are considered and investigated in this paper. Same reachable handling region of outlet air can be obtained for both air–water and air–liquid desiccant devices, which is among three boundary lines, isenthalpic line of inlet air, iso-relative humidity line of inlet fluid (water or desiccant), and the connecting line of inlet statuses of air and fluid. Inlet conditions of air and fluid affect heat and mass transfer characteristics to some extent, so that a zonal method is proposed only according to the relative statuses of inlet air to inlet fluid. Four zones, dehumidification zones A, D and regeneration zones B, C, are divided for air-desiccant direct-contact devices. The first three zones A, B and C are divided for air–water direct-contact devices, with the same zonal properties as those of air-desiccant devices. In order to obtain better humidification performance, fluid should be heated (in zone C) rather than air (in zone B). And fluid should be cooled (in zone A) rather than air (in zone D) to obtain better dehumidification performance. Counter-flow pattern should be applied for best mass transfer performance in the same conditions within the recommended zone A or C, while parallel-flow pattern is the best in zone B or D. [Copyright &y& Elsevier]

Cooling performance of two-stage indirect/direct evaporative cooling system is experimentally investigated in the various simulated climatic conditions. For this purpose, a two-stage evaporative cooling experimental setup consisting of an indirect evaporative cooling stage (IEC) followed by a direct evaporative cooling stage (DEC) was designed, constructed and tested. Due to the wide variety of climatic conditions in Iran, two air simulators were provided to simulate outdoor design condition of different cities in primary and secondary air streams. Results show that under various outdoor conditions, the effectiveness of IEC stage varies over a range of 55–61% and the effectiveness of IEC/DEC unit varies over a range of 108–111%. Aspects of achieving comfort conditions and power saving have been investigated with related excess water consumption. Considering the evaporative comfort zone, this system can provide comfort condition in a vast region in Iran where direct evaporative alone is not able to provide summer comfort condition. More than 60% power saving could be obtained by this system in comparison with mechanical vapor compression systems with just 55% increase in water consumption with respect to direct evaporative cooling systems. This system can fill the gap between direct evaporative cooling systems and mechanical vapor compression systems as an energy efficient and environmentally clean alternate. [Copyright &y& Elsevier]